Mammaglobin　may　be　a　potential　serum　biomarker　for　the　differential　diagnosis　of　breast　cancer.　260　serum　samples　were　collected　from　127　untreated　breast　cancer　patients　and　133　healthy　volunteers　to　analyze　the　sera　expression　of　mammaglobin　and　its　implications　for　both.　The　expression　vector　of　pGEX-4T-2-Mammaglobin　and　pBVIL1-Mammaglobin　were　constructed　and　transformed　into　E.coli.HB101　for　expression.　The　mice　were　immunized　with　the　purified　recombinant　protein　to　prepare　monoclonal　antibody　and　to　detect　by　ELISA　the　serum　of　normal　people　and　breast　cancer　patients.　Recombinant　mammaglobin　antigen　was　effectively　expressed　in　E.coli.　Two　hybridoma　cell　lines　were　obtained　after　the　mice　were　immunized　by　pGEX-4T-2-mammaglobin.　133　cases　of　normal　serum　and　127　cases　of　breast　cancer　serum　were　analyzed　by　ELISA.　The　sera　expression　level　of　mammaglobin　in　breast　cancer　group　(average　OD　value　0.645　+/-　0.223)　was　significantly　(p＜0.001)　higher　than　that　in　the　normal　control　group　(0.255　+/-　0.109).　Mammaglobin　has　a　higher　expression　in　the　serum　of　breast　cancer　patients　than　normal　control.　The　primary　results　indicate　that　mammaglobin　may　be　a　potential　serum　biomarker　for　the　differential　diagnosis　of　breast　cancer.